Filter system; element configuration; and methods

ABSTRACT

A filter element is includes a cylindrical media pack defining a central open volume and a longitudinal axis; a first end cap having a central aperture in flow communication with the central open volume; and a second, closed end cap having a central region closing an end of the media pack central, open volume. The closed end cap includes a projection extending axially outwardly therefrom and positioned at a location intersected by the longitudinal axis. An end cover for an air cleaner includes an inner side including a central projection thereon. Preferably, the central projection comprises a wall that includes an outer perimeter defining a regular polyhedron having at least five sides. An air cleaner comprises a cylindrical filter element having a first open end cap, a second closed end cap, and a cylindrical media pack extending therebetween. The first end cap defines an internal radial seal region. The second, closed end cap has a central region including a circular recessed portion. The air cleaner also includes an end cover. The end cover includes an inner side including a central projection thereon. The central projection is sized and shaped to matably engage the recessed portion of the second closed end cap, when the filter element is operably installed in the end cover. Methods for installing a filter element in an air cleaner preferably will use constructions as described herein.

This application is a continuation of application Ser. No. 10/721,934,filed Nov. 24, 2003, and issued as U.S. Pat. No. 6,837,920. ApplicationSer. No. 10/721,934 is a continuation of application Ser. No. 09/729,033filed Dec. 4, 2000, and issued as U.S. Pat. No. 6,652,614. Bothapplication Ser. No. 10/721,934 and 09/729,033 are incorporated hereinby reference.

TECHNICAL FIELD

The present invention relates to air cleaner systems. It particularlyconcerns air cleaners for air intake systems of combustion enginesand/or air compressor systems. In a typical application, the air cleanerwill be used in association with the air intake system for equipmentsuch as off road machinery (track-type tractors; truck loaders; skidsteer loaders; pipelayers; excavators; material handlers; wheeledexcavators; front shovels; forest machines; track skidders; drumcompactors (soil or asphalt); pneumatic compactors; asphalt pavers; soilstabilizers; cold planers; VFS trailers; wheel loaders; telescopichandlers; integrated tool carriers; wheel tractors; landfill compactors;soil compactors; backhoe loaders; articulated trucks; off highway trucksand tractors; scrapers; motor graders; wheel skidders; and generatorsets), farm equipment (tractors, combines), on mining equipment (orehaulers). The invention also concerns air filter elements, for suchsystems, and methods of assembly and use.

BACKGROUND

In general, the machinery vehicles or other equipment that operate withinternal combustion engines require filtration systems for the airintake to the engine. Such air filtration arrangements, typicallyreferenced by the term “air cleaner”, are generally positioned toseparate dust and other components from the air as it is drawn into theengine. Air cleaners typically include a housing and a replacementfilter element arrangement. Typically, the air cleaners are designedsuch that the filter elements can be removed and replaced.

Air compressor systems typically include two air lines that needfiltration: the intake air to the engine; and, the intake air to thecompressed air storage. Air cleaners are desirable for these systems aswell.

In general, improvement in air cleaners for such systems have beendesired.

SUMMARY OF THE DISCLOSURE

A filter element is disclosed that includes a cylindrical media packdefining a central open volume and a longitudinal axis; a first end caphaving a central aperture in flow communication with the central openvolume; and a second, closed end cap having a central region closing anend of the media pack central, open volume. In preferred constructions,the closed end cap includes a projection extending axially outwardlytherefrom and positioned at a location intersected by the longitudinalaxis.

An end cover for an air cleaner is also provided. The end cover mayinclude an inner side including a central projection thereon.Preferably, the central projection comprises a wall that includes anouter perimeter defining a regular polyhedron having at least fivesides.

An air cleaner is provided that comprises a cylindrical filter elementhaving a first open end cap, a second closed end cap, and a cylindricalmedia pack extending therebetween. The first end cap defines an internalradial seal region. The second, closed end cap has a central regionincluding a circular recessed portion. The air cleaner also includes anend cover. The end cover includes an inner side including a centralprojection thereon. The central projection is sized and shaped tomatably engage the recessed portion of the second closed end cap, whenthe filter element is operably installed in the end cover.

Methods for installing a filter element in an air cleaner preferablywill use constructions as described herein. Methods for changing thefilter element will also preferably use constructions as describedherein. Methods for cleaning air are provided.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a side elevational, partially fragmented, schematic view of anair cleaner mounted on an air flow tube on an air intake system.

FIG. 2 is an end view of the air cleaner of FIG. 1, but without the airflow tube and mounting bracket.

FIG. 3 is a side elevational, fragmented, enlarged view of the aircleaner depicted in FIG. 1.

FIG. 4 is a perspective view of a primary filter element usable in theair cleaner depicted in FIGS. 1–3.

FIG. 5 is an end elevational view of the filter element depicted in FIG.4.

FIG. 6 is an end elevational view of the primary filter element depictedin FIG. 4, and showing the opposite end as that shown in FIG. 5.

FIG. 7 is a cross-sectional view of the primary filter element depictedin FIGS. 4–6, the cross-section taken along the line 7—7 of FIG. 6.

FIG. 8 is an enlarged, cross-sectional view of the seal member of theend cap for the primary filter element, depicted in FIGS. 4–7.

FIG. 9 is a cross-sectional view of the air cleaner showing the primaryelement and safety element operably mounted in the air cleaner housing.

FIG. 10 is a fragmented, cross-sectional view depicting the housingcover being lined up with the end of the primary filter element.

FIG. 11 is a perspective view of the outer portion of the end cover ofthe air cleaner.

FIG. 12 is a perspective view of the inside of the end cover for the aircleaner.

FIG. 13 is a top plan view of the end cover depicted in FIG. 12.

FIG. 14 is a bottom plan view of the end cover shown in FIGS. 12 and 13.

FIG. 15 is a cross-sectional view of the end cover depicted in FIGS.11–14, the cross-section being taken along the line 15—15 in FIG. 14.

FIG. 16 is a perspective of the safety element.

FIG. 17 is a side elevational view of the safety element depicted inFIG. 16.

FIG. 18 is an end elevational view of the safety element depicted inFIG. 16.

FIG. 19 is a cross-sectional view of the safety element depicted inFIGS. 16–18 and taken along the line 19—19 of FIG. 18.

FIG. 20 is a fragmented, cross-sectional view depicting the primaryelement and safety element being aligned, during mounting of the primaryelement in the air cleaner.

FIG. 21 is a fragmented, cross-sectional view showing the safety elementand the primary element in proper alignment with each other.

DETAILED DESCRIPTION I. Air Filtration Systems—Generally

In general, air filtration systems for such equipment as off-roadequipment, farm equipment, mining equipment and over the highway trucks,include at least one removable and replaceable filter element, mountedinside an installed air cleaner housing. In many systems, two filterelements are used, both of which are removable and replaceable, with afirst filter element positioned as an upstream or primary element, and asecond filter element positioned as a downstream, secondary or safetyelement.

Attention is directed to FIG. 1, wherein certain external features of atypical air cleaner system or assembly are depicted. Referring to FIG.1, the reference number 1 depicts the air cleaner. The air cleaner 1comprises a housing 3 mounted, for example, by a mounting bracket 4 to aframe member 5 of appropriate equipment. The equipment would typicallycomprise a vehicle such as a truck, off-road construction equipment,tractor or similar vehicle; or, a stationary generator set or aircompressor.

The housing 3 of a typical air cleaner 1 is generally defined by twoprimary sections or segments: i.e. main body 8, and removable service oraccess cover 9. The access cover 9 provides for service access to aninterior of the main body 8, for servicing. For an air cleaner 1 of thegeneral type depicted in FIG. 1, servicing generally involvesdismounting and removing from the housing 3 at least one internallyreceived filter element, either for refurbishing or replacement.

The housing 3 of the air cleaner 1 depicted includes outer wall 11, airinlet 12 and outlet 13. For the preferred embodiment shown, the inlet 12and outlet 13 are both in the main body 8. In typical use, ambient orunfiltered air enters the air cleaner 1 through inlet 12. Within the aircleaner 1, the air is passed through a filter arrangement, describedbelow, to obtain a desirable level of particulate removal. The filteredair then passes outwardly from the air cleaner 1 through outlet 13, andis directed, by appropriate ductwork or conduits, to an inlet of an airintake for an associated engine or compressor or other system.

The particular air cleaner 1 depicted has outer wall 11 defining abarrel shaped or generally cylindrical configuration. In this particularconfiguration, the outlet 13 can be described as an axial outlet, sinceit generally extends in the direction of, and circumscribes, axis 15;axis 15 being a longitudinal central axis defined by an internallyreceived primary element 25, as described below.

It is noted that the particular air cleaner 1 depicted in FIG. 1, asseen from the end view of FIG. 2, is somewhat “obround”, i.e. slightlyoff round from cylindrical. Such configurations are well known, as arehousings that are more perfectly cylindrical. Herein, both types will bereferred to as “generally cylindrical.”

Access cover 9 generally fits over an open end 19 of body 8. In theparticular arrangement shown, access cover 9 is secured in place overend 19 by latches 20.

Because the particular arrangement 1 depicted is slightly obround, it isdesirable to ensure proper alignment between the end cover 9, and aremainder of the housing body 8. Proper radial alignment can be obtainedby engagement between a notch 20 a (FIGS. 11–13) on the cover 9, and apost on the housing body 8.

The particular air cleaner 1 depicted is shown mounted in a generallyhorizontal configuration, i.e. with axis 15 extending generallyhorizontally (assuming the equipment is standing on level ground andwith frame section 5 extending generally parallel to the ground).However, it is recognized that air cleaners 1 of the type depicted canbe used in other orientations.

Attention is directed to FIG. 3, in which portions of the assembly 1 aredepicted broken away, for viewing of selected internal detail. Referringto FIG. 3, it can be seen that the body 8, along with side portions 20of the cover 9, defines interior 22 of the air cleaner assembly 1.Within the interior 22 for the particular air cleaner 1 depicted ispositioned an air filter arrangement 23, through which air is directedduring use. The particular air filter arrangement 23 shown includes afirst or primary filter element 25 and a secondary or safety filterelement 26.

For the particular arrangement shown, the filter elements 25 and 26 arecylindrical in configuration, and thus have an outer circular periphery.The housing body, being slightly obround, then, does not define aperfect central longitudinal access in alignment with the filterelements 25, 26. Such arrangements, again, are common. However, it isalso common to have both the housing and the filter element havecircular outer perimeters, and the same central longitudinal axis.

Herein, the terms “filter element” or “element” are used to refer to aremovable, replaceable component (with respect to housing 11) thatincludes filter media through which the air being filtered passes, asthe air is directed: (1) from the inlet 12; (2) through interior 22; (3)to the outlet 13; in general with the element performing an airfiltration (or dust removal) function. Unless otherwise stated, theterms “element”, “filter” and “filter element” are meant to refer to aremovable and replaceable component within the air cleaner assembly 1.Generally and preferably, filter elements are configured such that theycan be removed and replaced by hand, at appropriate service intervals.This will be described in greater detail below.

Herein, the terms “primary element” and “main element” are generallyused to refer to a filter element on which a majority of dust loadingoccurs during air cleaner use. In typical systems that have twoelements, the primary element is positioned upstream from the secondaryor safety element, during typical assembly. By “upstream” in thiscontext, it is meant that, due to filter element position, air cleanerconfiguration, and the location of seals during use, air generally mustpass through the primary element before the air passes through thesafety or secondary element, when the air moves from the inlet 12 to theoutlet 13.

Herein, the terms “secondary element” or “safety element” are usedinterchangeably, and refer to a downstream element from the primaryelement. Typically, very little dust loading occurs on the secondary orsafety element, and generally only as a result of either: failure ofsome portion of the primary element or a seal; inadvertent dust movementduring servicing of the primary element; or some mishap.

Referring to FIG. 3, for the air cleaner 1 depicted, both the primaryelement 25 and the safety element 26 are generally cylindrical inconfiguration, each having an open cylindrical interior and a circularouter periphery (in cross-section). The two elements 25, 26 areconfigured such that the primary element 25 is mounted in a mannercircumscribing the safety element 26. This general configuration of acylindrical primary element 25 being mounted over a cylindricalsecondary element 26 has been used in a variety of equipment, and isdescribed, for example, in the following patents: U.S. Pat. Nos.6,051,042; 6,099,606; each of which is incorporated herein by reference.

Referring to FIG. 3, the assembly 1 includes an interior mounting ringor sealing ring 29. The seal ring 29 is a portion of an outlet flowconstruction or tube 29 a (FIG. 1), in flow communication with outlet13. More specifically, ring 29, wall section 29 b and outlet projection29 c collectively form outlet tube 29 a for exit of filtered air fromthe air cleaner 1.

In general, for the arrangement 1 shown, the safety element 26 ismounted to seal against an interior surface 30 of the mounting ring 29(or tube 29 a), and the primary element 25 is mounted to seal against anexterior surface 31 of the mounting ring 29 (or tube 29 a).

The seal 32 formed between the primary element 25 and the outer surface31 of the seal ring 29, will generally be referred to herein as “radial”because the sealing forces are directed radially toward and/or awayfrom, i.e. generally orthogonal to, axis 15. That is, the seal forcesare radially directed as opposed to being axially directed; “axial” inthis context meaning pointed in a direction generally parallel to axis15. The particular radial seal for element 25, is sometimes termed“interior” or “internal” because the radial seal 32 is located at aninterior of element 25.

A variety of types of radial seal systems are known. One of the mostwidely utilized radial seal systems for air cleaner assemblies of thetypes depicted in FIGS. 1 and 2, is the Donaldson Radialseal™ system,available from the Donaldson Company, Inc., of Bloomington, Minn., anddescribed generally in such references as EP 0329659; and U.S. Pat. No.5,547,480; each of these publications being incorporated herein byreference. The Donaldson Radialseal™ systems have been utilized onprimary elements for such equipment as off road machinery and vehicles,farm tractors, ore haulers, over-the-highway trucks; and, aircompressors.

The safety element 26 is also sealed to the seal ring 29 by a radialseal 33. In this instance, the radial seal 33 is an “exterior” radialseal, since it extends outwardly away from, and around, an outside ofelement 26, as opposed to being directed inside. Such seals aredescribed for example in U.S. Pat. No. 6,099,606, which is incorporatedherein by reference. Donaldson-manufactured safety elements using suchradial seals have been provided for such equipment as off road machineryand equipment such as tracked vehicles; wheeled equipment; rollercompactors; generator sets; and, ore haulers.

II. Two Potential Issues with Systems Similar to those Depicted in FIGS.1 and 2 A. Support for Horizontally Mounted Primary Elements

When the air cleaner system is generally as illustrated in FIGS. 1 and2, with the axis 15 extending generally horizontally, the filter element25 is also mounted generally horizontally. At the end 31 associated withthe outlet tube 13, the element 25 is generally well supported by themounting ring 29. However, at the opposite end, not shown in FIG. 2,there is generally no analogous structure to which the element issealed, to support the element in a horizontal configuration. Thus,typically, a support structure is desirable.

In certain prior radial seal systems, it was known to use an outercylindrical sleeve or shroud at this location, which supports theprimary element exteriorly, in position. Such shrouds are shown forexample, in U.S. Pat. No. 6,051,042 and U.S. Pat. No. 5,755,842, each ofwhich is incorporated herein by reference.

With respect to the issue of horizontal support, radial seal systemsdiffer significantly from axial seal systems. With axial seal systems,generally either a bolt arrangement or clamp arrangement is used toapply axial pressure to the element in some manner forcing the elementagainst an end of the housing. Such systems are shown, for example, inU.S. Pat. No. 3,488,928, which is incorporated herein by reference. Ingeneral, horizontal support for such systems is not required duringassembly, since the axial pressure keeps the element from moving. Insome instances, support arrangements are provided to facilitateappropriate positioning or centering of the element during assembly.

B. Alignment of the Safety Element

In general, servicing of arrangements such as those illustrated in FIGS.1 and 2 can be a problem, if the safety element 26 is not installed innear perfect axial alignment, since the primary element 25 must beinstalled over the safety element 26. This problem is exacerbated inlonger safety elements 26, i.e. elements at least 10 inches (25 cm) orlonger.

To help align the safety element, some safety element alignment systemshave been developed, see for example U.S. Pat. No. 5,800,581 and U.S.Pat. No. 3,488,928, each of the references being incorporated herein byreference.

III. The Primary Element

Attention is now directed to FIGS. 4–7, in which the primary element 25is depicted. The primary element 25 includes a side extension 34, openend 35, and closed end 36. In general, the side extension 34 extendsbetween the open and closed ends 35, 36. The open end 35 generallydefines a central aperture 40, FIG. 7.

For the embodiment depicted, the primary element 25 includes a first endcap 41 and a second end cap 42, with filter media pack 43 extendingtherebetween. In general, the first end cap 41 defines a first, or openend 35; the second end cap 42 defines a second, or closed end 36; and,the media pack 43 defines the side extension 34. In typical systems, themedia pack 43 will be generally cylindrical with central axis 15. Avariety of constructions can be used for the media pack 43, a preferredone for certain applications being described hereinbelow.

For the arrangement 1 depicted, the first end cap 41 serves severalfunctions. For example, it defines central outlet aperture 40 and acentral sealing region 46 for sealing against surface 29 (FIG. 3), whenthe element 25 is installed. Also, the end cap 41 secures components ofthe media pack 43 together and inhibits air and dust leakage aroundthem.

In addition, structural features provided in the end cap 41 can provideperformance enhancements. More specifically, end cap 41 includes asegmented, raised ring structure 44, FIG. 6. When the end cap 41 ismanufactured from a preferred soft compressible polyurethane, forexample, of the type indicated below, the segmented ring 44 forms abumper type extension at end 35 of element 25. This can provide anon-sealing, cushioning, against wall 11 of housing 3 (FIG. 1).

In typical preferred systems, the first end cap 41 is a single, unitary,molded material, preferably a soft compressible material; mostpreferably, a compressible, foamed, polyurethane. Preferred materialsand characteristics are provided herein below. Preferably the structuralfeatures of the end cap 41, then, are provided during a molding processat the same time that the media pack 43 is potted in, or secured to, thematerial of end cap 41. A general approach to this construction is alsodescribed below.

For certain arrangements, the seal region 46 will be shaped orconfigured analogously to other Donaldson Radialseal™ systems. Suchconfigurations are described and shown for example in EP 0329659; U.S.Pat. No. 5,547,480; U.S. Pat. No. 6,099,606; and especially WO9942719A2.The complete disclosures of each of these references are incorporatedherein by reference.

Attention is directed to FIG. 8, which shows a fragmented, blow-upcross-section of a three step or three stage radial seal configurationusable in the element 25.

More specifically, radial seal region 46 includes: (moving from outsideof the element inwardly), three ring or steps 37, 38 and 39, ofsequentially decreasing diameter. As a result, positioning of theelement 25 over the outlet tube 29, is facilitated since the compressionoccurs in consecutive steps of increasing resistance.

The radial seal region 46 is preferably constructed and arranged tocompress at least 12% of its thickness, i.e. the distance between theouter surface 39 a when uncompressed, and the inner surface 43 a of themedia pack, the inner surface 43 a typically being defined by an innerliner. Preferably, the compression is by an amount of at least 15% ofits thickness, typically 20 to 33% of its thickness.

Again, because of the soft compressible nature of the material of endcap 41, (especially the material in region 46), when the primary element25 is installed on the seal ring 29, the material in region 46 iscompressed against the exterior surface 31; generally with thecompression being controlled and contained by a portion of the mediapack 43, typically an inner liner as characterized below.

The second end cap 42, defines the closed end 36 of the primary element25. The second end cap 42 also serves a number of functions. Forexample, end cap 42 operates to retain the media pack 43 together andsealed at closed end 36. This operation is generally conducted by outerannular region 49 of the second end cap 42. In addition, portions of thesecond end cap 42 operate to provide extension across otherwise openinterior 50 of primary element 25, to close end 51 to passage ofunfiltered air therethrough. This function is performed by central area53 of the second end cap 42. By “closed end”, it is meant the end cap 42prevents passage into or out of the filter interior 50; a closed endincludes an end cap with a hole plugged by something carried by thefilter element, for example.

As will be indicated below, the annular region 49 may comprise either asoft compressible material or a hard material. Preferably, the annularregion 49 includes a plurality of segments 52 projected axiallyoutwardly therefrom, to form a non-sealing, engagement with cover 9,during installation, FIG. 10.

The preferred second end cap 42 depicted includes features providing foradditional functions. One function relates to appropriate configurationfor support of the primary element 25, when mounted in a horizontalposition as indicated in FIGS. 1 and 2. This function is performed inpart by central rim 55 as described below. Also preferably, portions ofsecond end cap 42 provide for an alignment and support function incooperation with the safety element 26. For the particular arrangementshown, this function is provided by safety element engagement portion56, as described below.

For the particular arrangement depicted, the second end cap 42 is a twocomponent end cap, with the first component comprising molded polymericmaterial which defines annular region 49 and a second componentcomprising a preformed structure 58 which defines central rim 55,central region or area 53, and safety element engagement portion 56. By“preformed” in this context, it is meant that the structure 58preferably comprises a rigid material preformed to possess a preferredconfiguration and that is then secured into the overall primary element25, during a step of element construction, described below, prior tomolding outer annular region 49. Preformed structure 58 is described ingreater detail below.

IV. Support of the Primary Element Second or Closed End, During AirCleaner Use

As indicated above, features of the primary element 25 facilitatesupport of the element-closed end 36 when installed for use, especiallyin the horizontal position depicted in FIGS. 1 and 2. With respect tothis function, attention is directed to FIGS. 9–15.

Referring first to FIGS. 11–15, end cover 9 is depicted. The end cover 9includes an outer surface 65 and an inner surface 66. When installed,the outer surface 65 of the cover 9 is the surface generally directedtoward the exterior environment, and the inner surface 66 is generallydirected toward the air cleaner interior 22.

Referring to FIGS. 12 and 13, the inner surface 66 includes an elementengagement construction 70 thereon. The element engagement construction70 is generally constructed and arranged to interlock or supportinglyengage, abut or align with end 36 of element 25, when the cover 9 ispositioned on an air cleaner 1 having the preferred primary element 25installed. For the particular arrangement shown, the element engagementconstruction 70 comprises a projection 72, which projects into recess 74of end cap 42, during installation. Preferably the projection 72 issized and configured to supportingly abut, engage or align with centralrim 55 during installation, during assembly. (It is noted that actualcontact between projection 72 and rim 55 is not required, if thealignment is adequately close to ensure that the element 25 cannot moveor rock downwardly undesirably far, typically, for example, no more than20 millimeters.) It is noted that if only a few millimeter spacing orless is maintained, shortly after assembly, the main element will tendto settle until engagement actually occurs, typically either as a resultof vibrational forces when the equipment is running, or added weight inthe element due to particulate load with use.

For the particular preferred system depicted, central rim 55 is circularand thus defines circular recess 74. In preferred systems, the centralregion 53 is circumscribed by the media pack 43. Preferably, the centralrim 55 includes an annular wall 57 with a projection segment 57 a.Preferably, the projection segment 57 a projects into the central openvolume 50 from the second end 36 of the media pack 43 an axial distanceof at least 6 mm, typically 12–25 mm, and no greater than 200 mm. Theprojection segment 57 a may be angled or slant toward the interior 50,but by no more that a certain radial distance from the inner edge of themedia pack 43 such that it would prevent fitting with the air cleanerend cover 9. Preferably, the projection segment 57 a becomes radiallyspaced no further than 50 mm from the media pack 43 along a distance ofinward axial projection of at least 6 mm. In the particular one depictedin the FIGS., segment 57 a becomes radially spaced no further than 1–15mm along a distance of inward axial projection of 12–25 mm. It should benoted that, in alternate embodiments, other portions of the annular wall57 may be radially spaced from the media pack 43 longer than 50 mm.

Example dimensions include: the rim 55 having a diameter of at least 125mm, typically 150–180 mm, and no greater than 300 mm. The recess 74preferably has a depth (or height) (measured from rim 162 to planarregion 158) of at least 6 mm, typically 12–25 mm, and no greater than200 mm.

Preferably, an outer perimeter 75 of projection 72 is non-circular, forreasons that will be described below. Most preferably outer perimeter 75includes at least three vertices or apices 79. Preferably, outerperimeter 75 defines a polyhedron which is sized and configured toengage, abut or become positionably aligned with circular central rim 55at spaced points or vertices 76. Regular polyhedral shapes, i.e.polyhedrons having straight segments or sections 78 all of equal length,and defining spaced apices 79, are preferred. Most preferably, thepolyhedral perimeter 75 has at least five sides and not more than tensides, defining at least five and not more than ten apices. Theparticular projection 72 depicted in FIGS. 12 and 13 is octahedral.

Preferably, projection 72 is configured so that if it does not abutcircular central rim 55, the apices 79 are spaced from the central rim55, when the air cleaner 1 is assembled, by not more than 30millimeters, and preferably not more than 15 millimeters. This willensure that, when installed, the element 25 cannot rock downwardlyundesirably far.

Preferably, the projection 72 will be continuous in extension, i.e.without gaps, so that it is fairly strong and not likely to break inuse. However, discontinuous configurations can be used. Also,preferably, the projection 72 defines a hollow, recessed, interior 82which, among other things, allows receiving room for certain additionalfeatures of the element 25 characterized below. Preferably, perimeter 75comprises a continuous wall: (a) at least about 0.25 millimeters thick,typically 0.5 to 5 millimeters thick, no more than 20 mm thick; and (b)at least 10 millimeters high, typically 20 to 50 millimeters high, nomore than 100 mm high.

By reference to FIGS. 9 and 10, it will be apparent that after theelement is installed, once the cover 9 is put in place, projection 72will extend into recess 74. In general, any upwardly directed apices,for example apex 83, FIG. 9, will support the element 25 and prevent theelement 25 from undesirably sagging, rocking or dropping at end 36. Forpreferred arrangements, the parts are configured such that projection 72extends at least 5 millimeters into recess 74, most preferably 10 to 30millimeters, and not more than 100 mm. FIG. 9 also shows the safetyelement 26 installed in the system.

From an evaluation of FIGS. 9 and 10, certain advantages to particularconfigurations of annular region 49, and perimeter 75 will be apparent.Since the preferred annular area 49 is circular, the relative radial(rotational) position of the element 25 on ring 29 when installed, willmake no difference, with respect to engagement by the end cover 9. Thatis, no matter how element 25 is radially oriented, it is generallyradially symmetric with respect to axis 15, when installed, at leastwith respect to the configuration of rim 55.

If the housing were actually cylindrical instead of slightly obround,the preferred shape or configuration characterized with respect to theprojection 72 and perimeter 75, would allow for variations in radialorientation of the end cover 9 on end 19. In particular, when theprojection 72 contains at least five apices, equally spaced so, if thecover 9 were round, no matter how cover 9 was radially oriented on body8, in closing the end 19, at least one apex would be directed generallyupwardly. However, with the obround configuration, the cover 9 has afixed configuration relative to the body 8, so the apices are orientedon the cover 9 to ensure that at least one is directed upwardly, whenthe construction is operably assembled.

It is preferred that the perimeter 75 not be round, for several reasons.First, if the perimeter 75 is not round, persons will be unlikely to tryto seal an element to the perimeter 75, which can lead to aninappropriately assembled air cleaner 1. Also, a non-round structurewill be relatively strong and self-supporting and will be fairlystraight forward to manufacture to appropriate specification.

V. Other Features of End Cover 9

Attention is directed to FIGS. 11 and 14, with respect to end cover 9.External surface 65 generally includes flat central region 84. Surface65 also includes stepped regions 85, with molded gussets 86 for support.As noted, the central region 84 is offset from concentric alignment withouter perimeter rim 87 (FIG. 14). This is so that the end cover 9 canmatch alignment in certain already existing air cleaner bodies.

As indicated above, certain other existing equipment uses a roundhousing, in which case the central axis for the projection 72 can bepositioned in line with a central axis for the outer perimeter of thecover.

Attention is directed to FIGS. 12 and 13. Inner surface 66, centralregion 67 includes, projecting inwardly therefrom, wall 75 as well asradially extending strengthening ribs 68. Ribs 68 extend radially fromthe wall 75 to the outer perimeter rim 87.

VI. Arrangement for Safety Element Alignment

As indicated above, the preferred air cleaner 1 includes an arrangement76 (FIGS. 20, 21) for ensuring appropriate alignment of the safetyelement 26 with the primary element 25.

The safety element alignment is one which does not require any structureon the seal ring 29, or indeed any additional structure on the housing3, but rather operates with features on the elements 25, 26. Thus, itcan be retrofit into previously existing housing bodies.

In general, the alignment arrangement 76 includes a projection/receiverarrangement 88 with a first member 89 of the projection/receiverarrangement 88 positioned on the primary element 25, and a second member90 of the projection/receiver arrangement 88 provided on the safetyelement 26. For the particular arrangement shown, the primary element 25includes a receiver member 92 in end cap 42; and the safety element 26includes a projection member 93, on end cap 105.

Attention is directed to FIGS. 16–19, in which the safety element 26 isdepicted. The safety element 26 includes a first open end 100, anopposite closed end 101, and a side extension 102. For the particulararrangement shown, the open end 100 is defined by a first open end cap104; the closed end 101 is defined by a second closed end cap 105; andthe side extension 102 is defined by a media pack 106 that is embeddedin, and extends between, the two end caps 104, 105. The particulararrangement shown also includes an inner liner 120 and an outer liner121, extending between the two end caps 104, 105. In alternatearrangements, the inner and outer liners 120, 121 may be omitted. InFIGS. 19–21, only a partial section of the inner liner 120 is depicted.

For the particular embodiment shown, the open end cap 104 provides thefunctions of: retaining the media pack sealed and assembled, at the openend 100; and, sealing seal region 108 (as an externally directed radialseal) to ring 29, when assembled. For preferred arrangements, end cap104 is a unitary molded material comprising a soft compressible polymer,preferably foamed polyurethane. Preferred materials and materialcharacteristics are described below.

The second end cap 105 also performs several functions. For example, itsecurely encloses end 101, and retains the media pack 106 sealed andassembled at that end. Also, the closed end cap 105 is oriented toextend adjacent to, and in some instances abuts, the primary element 25,so that the safety element 26 does not back away from end 110 (FIG. 1)of air cleaner 1, in use, once the primary element 25 has beeninstalled.

For the preferred embodiment shown, another function provided by thesafety element 26 is that it includes a portion of theprojection/receiver arrangement 88, which engages a mating member on theprimary element 25, to ensure appropriate axial alignment of the safetyelement 26, during assembly.

More specifically, the safety element 26 includes second member 90 ofthe projection receiver arrangement 88. For the particular arrangementshown, the second member 90 comprises projection member 93.

Preferred projection members are configured to have an outer perimeter111 which includes some degree of radial symmetry, so that radialalignment of the safety element 26 is not critical to proper function ofthe projection/receiver arrangement 88. The particular preferredprojection 93 depicted is a frustoconical member 112, having conicalsidewall 113 and end 113 a.

As described below, the preferred primary element 25 includes anappropriately sized and shaped receiver 92, for the frustoconical member112.

More specifically, and referring to FIGS. 20–21, the primary element 25includes a receiver member 92 constructed, arranged and oriented toreceive frustoconical member 112 therein, during assembly. A preferredreceiver member 92, for a frustoconical projection member 112, is afrustoconical receiver 114, comprising conical sidewall 115 and end 116.

Operation of the projection/receiver system 88, to facilitate alignmentbetween the safety element 26 and the primary element 25 will beunderstood from the schematic depictions of FIGS. 20 and 21.

Referring to FIG. 20, the safety element is indicated at 26, and themain element at 25. The elements 25, 26 are shown with the safetyelement 26 out of perfect alignment with central axis 124. As a resultof the misalignment, as the primary element 25 is moved in the directionof arrow 125, projection 93 of safety element 26 is engaged by receiver92, again out of perfect axial alignment. However, a cam or slidingengagement between the surfaces 130 and 131, as primary element 25continues to be moved in the direction of arrow 125, from the positionshown in FIG. 20, will align the elements 25, 26. In particular,engagement between the surfaces 130 and 131 will force the safetyelement 26 to straighten out or reorient itself, into the alignmentshown in FIG. 21. Alternately phrased, preferably theprojection/receiver combination 92/93 is oriented such that whenmisalignment occurs, continued motion along the direction of a centralaxis for the primary element 25 will tend to cause the safety element 26to slide into appropriate alignment. It is noted that engagement betweenthe projection 93 and receiver 92, at the end of the alignment, FIG. 21,will also tend to retain the safety element in proper alignment, atleast until the primary element 25 is removed.

It is preferred that the projection 93 and the receiver 92 each havesufficient circular symmetry (although not necessarily the same shape)so that relative radial orientation between the safety element and theprimary element do not matter, for functioning of theprojection/receiver assembly. The frustoconical configuration indicatedis preferred but is not required. Alternative usable shapes include:cylinders, cubes, boxes, truncated spheres, hemispheres, and 3-dstructures having cross-sections of triangles, pentagons, octagons, orother polyhedrons.

Preferred dimensions for the frustoconical projection 93 are providedherein: a height from end cap outer surface 107 to end 113 a of at least5 millimeters, typically 10–50 millimeters, and not greater than 100 mm;a base diameter, that is, the diameter at its largest section coplanarwith end cap surface 107 of at least 25 millimeters, typically 30–80millimeters, and not greater than 150 mm; and a diameter at its end 113a of at least 5 millimeters, typically 10–30 millimeters, not greaterthan 80 mm. The sidewall 113 extends at an angle between the basediameter and the end 113 a at least 0.5°, typically 1–45°, and notgreater than 80°. The receiver 92 is preferably sized to receive theprojection 93 without interference. As such, the receiver 92 may besized on the order of 5–20% larger than the above dimensions (i.e.: aheight (or depth, depending on perspective) of 11–40 mm; a diameter atits largest section (open end) of 33–100 mm; and a diameter at itsclosed end of 11–40 mm).

VII. Methods of Forming the Primary Filter Element

In FIG. 7, media pack 43 is depicted. Media pack 43 includes an innerliner 151 and a cylindrical extension of filter media 152 thatcircumscribes the inner liner 151. For a preferred system, the innerliner 151 and extension media 152 are the same length. In FIG. 7, theinner liner 151 is shown fragmented. It should be understood that if aninner liner is used, the liner will line the entire inner portion of thefilter media 152.

During typical assembly, the cylindrical extension of filter media 152will be constructed and then be slid over inner liner 151. A later stepof manufacture is an engagement between the media pack 43 and centralend cap member 160. In a final molded construction, central end capmember 160 will serve to form and define the following features: centralarea 53 of the closed end cap 42; central rim 55; and, receiver 92.

Preferably, the central end cap member 160 has a bowl shape 161, with anoutwardly projecting rim 162, central receiver 92, and planar region158. In the particular embodiment depicted, planar region 158corresponds to an outer surface portion of the end cap 42 that is mostrecessed relative to remaining portions of the end cap 42. Preferably,the recessed sidewall 163 of the bowl 161 has an outer circularperiphery 163 a (FIG. 10) with an outside diameter slightly larger thanan inside diameter of inner liner 151, so as to cause an interferencefit when the inner liner 151 is pressed over sidewall 163.

The assembly comprising central end cap member 160 and media pack 43 isthen positioned in a mold, into which is also positioned a resin forforming a remainder of the closed end cap 42.

The opposite open end cap 41 can be formed either before or after theclosed end cap 42. In general, the open end cap 41 would be formed byplacing an appropriate end of the media pack 43 into a mold, with resinto form the end cap. Preferred central end cap member 160 will comprisemolded, rigid plastic, constructions.

VIII. Preferred Methods of Forming the Safety Filter Element

The safety filter element 26 can generally be manufactured in accordwith previously applied manufacturing techniques, except formodifications to manage the configuration of the member of theprojection/receiver arrangement 88 position on the closed end 101 of thesafety element 26. Preferably the closed end 101 of the safety element26 is formed from a molded plastic, such as urethane having a hardnessof 30 Shore D.

Typical methods of preparation, then, would involve assembling the mediapack; placing a first end in a mold, with resin, to mold the closed endcap; and placing a second end in a mold, with resin, to form the openend cap.

As to the open end cap having the external directed radial seal thereon,resin capable of forming upon cure, and appropriately soft, compressiblepolyurethane end cap of the same type as would be used to form the firstend cap having the radial seal thereon for the primary element, wouldgenerally be preferred. A preferred such material is characterizedbelow.

IX. Preferred Media Packs

The preferred media pack for the primary and safety element will, inpart, depend upon specifications and efficiency needs for the engine orother system involved. Herein, a preferred primary element media packwill be described, which was developed specifically to lead to enhancedperformance for certain types of off road construction equipment, farmequipment, and mining equipment, as characterized.

In particular, the following equipment has utilized the DonaldsonRadialseal™ system for a number of years: Caterpillar tractors, wastehandling arrangements, truck loaders, skid steer loaders, pipelayers,excavators, material handlers, front shovels, forest machines, trackskidders, compactors, pavers, soil stabilizers, planers, combines, VFStrailers, backhoe loaders, off highway trucks, off highway tractors,skidders, scrapers, and motor graders.

The system installed, however, in that equipment, generally: (1) has nothad an alignment system to support or bias the safety element intoappropriate alignment, as engagement with the primary element occurs;and (2) has been limited in lifetime due to restriction buildup as dustis loaded on the system.

In developing the preferred elements characterized herein, Donaldsonmade efforts to expand substantially the duration of operation lifetimefor elements in such equipment without modifying the size andconfiguration of the air cleaner body; and, without seeking modificationof the engine specifications or operation.

A new element construction, for longer performance, is now presented. Ingeneral terms, the media construction comprises two media segments: aninside pleated media section; and, an outer region of non-woven fibrousdepth media.

One particular useful construction is depicted in FIG. 7. In thisconstruction, the primary element has first open end cap 41, comprisingsoft compressible foam polyurethane in accord with the specificationsgiven below; second end cap 42 manufactured in accord with the methodindicated above and comprising a composite of: a central bowl 161 moldedfrom rigid plastic; and an outer annular region molded from urethane.The media pack comprises inner liner 151 which is porous; immediatelysurrounded by a pleated media region 177 having a pleat depth of atleast 25 mm, typically 50–100 mm. Preferably the pleated media 177comprises paper or cellulose. One type of pleated cellulose usable inconstructions described herein has the following properties: a basisweight of 63–71 lbs./3000 ft²; a thickness of about 0.013 inch; a poresize of about 88 microns; a corrugation of 0.015–0.021 inch; a drytensile strength of 12–28 lbs./in.; a wet tensile strength of 3–13lbs./in.; a wet burst strength of 15–35 psi; a Frazier permeability of50–64 ft./min. Preferably, the inner liner comprises expanded metal, butmay also be non-metallic such as plastic.

Positioned outside of the pleated media is a cylindrical extension offibrous depth media 178, preferably an air laid polyester fiber mediahaving thickness within the construction of 0.25–1 inch. In particularmedia having the following properties is usable: a weight of 4.6–5.6oz./yd.²; and a permeability of 900 ft./min.

In the particular arrangement shown, the extension of depth mediacomprises a single wrap of material such as fibrous depth media,stitched to form seam 180. Alternative methods of securing thecommercially available depth media 178 in a cylindrical configurationcan be used.

It is noted that a variety of alternate constructions of depth media canbe provided, for example, multilayered systems, gradient systems, etc.However, the particular construction shown, with specifications asindicated below, leaves a substantial improvement when installed in apreviously existing air cleaner. In some arrangements, it may bedesirable to secure or support the pleated media 177 with a narrow bandaround the circumference of the pleat tips. If a band is used, the bandwill be applied before the outer wrap 178 is placed over the pleatedmedia 177.

Attention is again directed to FIG. 7. FIG. 7 shows the entire mediapack 43 as embedded or molded in each of the end caps 41, 42. It can beseen that the sleeve of depth media 178 is tucked into the end cap 41 attuck 181. Similarly, the opposite end of the sleeve of fibrous depthmedia 178 is tucked into end cap 42 at tuck 182. In the arrangementshown in FIG. 7, it is contemplated that the entire media pack 43including both the pleated media 177 and the depth media 178 is embeddedin each of the end caps 41, 42 as a total unit, which results in thetucked regions 181, 182. In alternative methods of constructions, onlythe pleated media 177 will be molded within and embedded in the oppositeend caps 41, 42. In this alternative arrangement, the depth media 178 isthen wrapped around the resulting construction of the pleated media 177embedded in the opposite end caps 41, 42.

Preferably, the end cap 41 and the end cap 104, which form the sealingregions 46, 108 respectively, are constructed of molded foamedpolyurethane. One example material has the following properties: atensile strength of 110 psi minimum; an elongation of 200% minimum; atear strength of 15 lbs./in. minimum; a compression deflection at 70° F.of an average of 7–14 psi; a compression deflection after heat aging 7days at 158° F. of +/−20% change from original deflection values; acompression deflection at cold temperature of −40° F. of 100 psimaximum; a compression set after heat aging 22 hours at 158° F. of 10%maximum; and after heat aging 22 hours at 180° of 25% maximum

X. EXAMPLES

One example primary element has the following dimensions: an overalllength of at least 225 mm, typically 300–385 mm; an inner diameter atits open end cap of at least 125 mm, typically 150–255 mm; an insidediameter of the bowl 161 of at least 125 mm, typically 150–180 mm; aheight of the receiver member 92 of at least 6 mm, typically 12–25 mm;an outermost diameter of the receiver 92 of at least 25 mm, typically37–75 mm; an overall outer diameter of at least 200 mm, typically280–385 mm.

One example safety element 26 has the following dimensions: an overalllength of at least 125 mm, typically 255–385 mm; an outermost diameterof at least 75 mm, typically 125–200 mm; an inside diameter of at least50 mm, typically 75–125 mm; and a height of projection member 93 of atleast 6 mm, typically 12–20 mm.

One example end cover 9 has the following dimensions: an outermostdiameter of at least 150 mm, typically 300–400 millimeters; a depth ofat least 20 mm, typically 40–100 millimeters; a polyhedral wall formingthe outer perimeter 75 having a height of 20–60%, typically 30–50% ofthe overall height of the end cover, at least 5 mm, typically 10–40millimeters.

1. A filter arrangement comprising: (a) a primary filter elementcomprising: a first, open end cap; a second end cap; and a media packextending therebetween; (i) said first, open, end cap defining aninternal radial seal region; and (ii) said second end cap having acentral region including a recessed portion having an outermostdimension of at least 125 mm and a recess of at least 6 mm; (iii) saidsecond end cap including a projection extending axially from a center ofsaid central region; and (b) a safety filter element mounted in aninterior of said primary filter element; (i) said safety element havingan open end cap, a closed end cap, a region of filter mediatherebetween; (ii) said safety element closed end cap including aprojection extending axially therefrom; and (iii) the safety element andprimary element engaging to ensure axial alignment of the safetyelement.
 2. A filter arrangement according to claim 1 wherein: (a) saidprimary filter element defines a receiver in said central region of saidsecond end cap; and (i) said safety element closed end cap projectionextending into said receiver.
 3. A filter arrangement according to claim1 wherein: (a) said safety element open end cap includes an annular,externally directed radial seal portion.
 4. A filter arrangementaccording to claim 1 wherein: (a) said primary filter element second endcap projection extends axially outwardly from said central region.
 5. Afilter arrangement according to claim 1 wherein: (a) said safety elementclosed end cap projection extends axially outwardly therefrom.
 6. Afilter element comprising: (a) a cylindrical media pack defining acentral open volume; (b) a first end cap having a central aperture inflow communication with said central open volume; (i) said first end capincludes an annular, external, radially outwardly directed radial sealportion; (c) a second, closed, end cap having a central region closingan end of said media pack central, open, volume; (i) said closed end capincluding a frustoconical projection; (A) said frustoconical projectionhaving a generally circular base with a diameter of at least 25 mm; (B)said frustoconical projection extending axially from said closed end capat least 5 mm.
 7. A filter element according to claim 6 wherein: (a) thefrustoconical projection extending axially outwardly from said closedend cap.
 8. A filter element according to claim 6 wherein: (a) thefilter element has an overall length of at least 125 mm; an outermostdiameter of at least 75 mm; and an inside diameter of at least 50 mm. 9.A filter element according to claim 6 wherein: (a) said frustoconicalprojection has a height of 12–20 mm.
 10. A method of servicing an aircleaner; the method comprising steps of: (a) removing a removableservice cover from an air cleaner housing to expose an open end and afirst serviceable filter element; (i) the first serviceable filterelement comprising: (A) an extension of media having a first and secondend; the extension of media surrounding an open interior, extendingbetween first and second end caps; (1) the first end cap having acentral air flow aperture therein in fluid flow communication with theopen interior; (2) the second end cap being a closed end cap having noaperture therethrough and comprising: (I) a closed recess projectinginto the open interior from the second end of the media; (ii) the firstserviceable filter element being positioned with the closed end capdirected toward the open end; (b) removing the first serviceable filterelement from the air cleaner housing from a position mounted over afirst safety filter element by drawing the first serviceable filterelement outwardly from the housing, by passage through the open end; (c)positioning a second serviceable filter element within the air cleanerhousing, by passage through the open end and over the first safetyfilter element; (i) the second serviceable filter element comprising:(A) an extension of media having first and second ends; the extension ofmedia surrounding an open interior, extending between first and secondend caps; (1) the first end cap having a central air flow aperturetherein in fluid flow communication with the open interior; (2) thesecond end cap being a closed end cap having no aperture therethroughand comprising: (I) a closed recess projecting into the open interiorfrom the second end of the media; (ii) the step of positioning includingpositioning the second serviceable filter element within the housingwith the closed end cap directed toward the open end; and (d) mountingthe service cover with: (i) a projection on the service cover projectinginto the closed recess in the second end cap of the second serviceablefilter element.
 11. A method of servicing according to claim 10 wherein:(a) the step of positioning a second serviceable filter element includesarranging the second serviceable filter element to engage a portion ofthe first safety element.
 12. A method of servicing according to claim11 wherein: (a) the step of mounting the service cover includespositioning a recess in the projection of the service cover over andaround a frustoconical section of the second serviceable element.
 13. Amethod of servicing according to claim 10 wherein: (a) the step ofmounting the service cover comprises mounting the service cover with anon-circular projection having at least three vertices projecting intothe closed recess of the second end cap.
 14. A method of servicingaccording to claim 10 wherein: (a) after the step of mounting theservice cover, securing the service cover to the air cleaner housingwith latches.
 15. A method of servicing according to claim 10 wherein:(a) the step of positioning a second serviceable filter elementcomprises: (i) positioning a second serviceable element having afrustoconical section on the second end cap directed toward the openend; and (ii) arranging the second serviceable filter element to receivea portion of the first safety element projecting into the frustoconicalsection.
 16. A method of installing a filter element into an aircleaner; the method comprising: (a) providing a primary element having amedia pack defining an open volume, a first open end cap, and anopposite second end cap; (i) the second end cap being a closed end capwith no aperture therethrough and including a closed recess projectinginto the open volume; (b) orienting the primary element over a safetyelement; (i) the safety element having an open end cap, a closed endcap, and a region of filter media therebetween; (ii) the safety elementclosed end cap including a projection extending axially therefrom; (c)engaging the safety element and primary element to ensure axialalignment of the safety element; and (d) orienting an access coverhaving an inner side with a central projection thereon over the primaryelement by extending the central projection into the closed recess tosupport the primary element.
 17. A method according to claim 16 wherein:(a) the second end cap of the primary element has a central regionincluding a recessed portion having an outermost dimension of at least125 mm and a recess of at least 6 mm; (b) the primary filter elementdefines a receiver in the central region of the closed end cap; and (c)the step of engaging includes extending the safety element closed endcap projection into the receiver.
 18. A method according to claim 16wherein: (a) the step of orienting the primary element includes forminga radial seal between the first open end cap of the primary element andthe air cleaner.
 19. A method according to claim 16 wherein: (a) thestep of orienting an access cover includes using an access cover with anon-circular central projection.
 20. A filter arrangement comprising:(a) a primary filter element comprising: a first, open end cap; a secondend cap; and a media pack extending therebetween; (i) said first, open,end cap defining an internal radial seal region; and (ii) said secondend cap having a central region including a recessed portion having anoutermost dimension of at least 125 mm and a recess of at least 6 mm;(iii) said second end cap including a projection extending axially fromsaid central region; and (b) a safety filter element mounted in aninterior of said primary filter element; (i) said safety element havingan open end cap, a closed end cap, a region of filter mediatherebetween; (ii) said safety element closed end cap including aprojection extending axially therefrom; and (iii) the safety element andprimary element engaging to ensure axial alignment of the safetyelement; (c) said primary filter element defines a receiver in saidcentral region of said second end cap; and (i) said safety elementclosed end cap projection extending into said receiver.
 21. A filterarrangement according to claim 20 wherein: (a) said safety element openend cap includes an annular, externally directed radial seal portion.22. A filter arrangement according to claim 20 wherein: (a) said primaryfilter element second end cap projection extends axially outwardly fromsaid central region.
 23. A filter arrangement according to claim 20wherein: (a) said safety element closed end cap projection extendsaxially outward therefrom.
 24. A filter element comprising: (a) a first,open end cap; (i) said first, open, end cap defining an internal radialseal region; (b) a second, closed end cap at an end opposite to thefirst open end cap; (i) said second end cap having a central regionincluding a recessed portion having an outermost dimension of at least125 mm; (ii) said second end cap having a central region including arecess of at least 6 mm; and (iii) said second end cap including aprojection extending axially from a center of said central region; and(c) a media pack extending between the first and second end caps.
 25. Afilter arrangement according to claim 24 wherein: (a) said filterelement second end cap projection extends axially outwardly away fromsaid open end cap.